The goal of this proposal is to develop an effective magnetic resonance (MR) probe for noninvasive, molecular imaging of renal fibrosis. Renal fibrosis is a hallmark of all chronic kidney diseases (CKD). It is estimated that 500 million peopl worldwide are currently suffering from CKD and many of these patients will progress to end- stage renal disease (ESRD), a devastating disorder that requires dialysis or kidney transplantation. The incidence of ESRD has doubled over the last 25 years in the United States, and in fact, treatment of CKD and ESRD accounted for 27% ($60 billion) of Medicare expenses in 2005. Clinical studies have demonstrated a strong correlation between ESRD and the extent of renal fibrosis. Quantification of renal fibrosis should predict long-term outcome of renal function in CKD patients and could also be used to monitor response to new anti- fibrotic therapies. Currently, biopsy is the gold standard for diagnosing renal fibrosis. However, biopsy is not suitable for monitoring disease progression in CKD patients as it is invasive and subject to sampling error. Therefore, there is a major unmet medical need to develop noninvasive strategies to detect and monitor progression of renal fibrosis. This proposal is in response to RFA-DK-13-026, Novel Methods for Detection and Measurement of Organ Fibrosis in Kidney, Bone Marrow, and Urological Diseases. In particular it responds to the specific need for Novel minimally invasive imaging methods for the detection and measurement of organ fibrosis and to detect changes in fibrosis that quantify progression, stabilization, and/or regression over time and to Correlate fibrotic status with organ dysfunction, recovery, and/or regression Renal function progressively declines in response to the excessive accumulation of extracellular matrix proteins. Myofibroblasts secrete collagens, as well as the enzyme lysyl oxidase (LOX) which crosslinks the collagen fibrils. Recently, we have developed a prototype small molecule magnetic resonance (MR) probe, termed Gd-Hyd, with specificity to cross-linked collagen. In preliminary data we have demonstrated that Gd- Hyd can accurately detect renal, liver and pulmonary fibrosis in small animal models. Since LOX-mediated crosslinking of collagen is an aspect of active disease, our hypothesis is that molecular imaging of LOX-mediated collagen crosslinking accurately reflects renal fibrogenesis and thus can be used to detect renal fibrosis and monitor disease progression and response to therapy. The importance of these studies cannot be overstated as CKD is a major worldwide health problem. The accomplishment of our Specific Aims would lead to a new methodology for identifying fibrotic patients at high- risk for disease progression and poor survival and also for monitoring response to anti-fibrotic therapies.